This invention relates to a liquid fuel injection system and method for use in an internal combustion engine and is especially useful when an alternative fuel such as a gaseous fuel is to be employed in the place of gasoline.
The rapidly rising cost of gasoline during the last few years has encouraged interest in the use of alternative fuels in such engines instead of gasoline and one of the alternatives is a class of fuels referred to as gaseous fuels. By gaseous fuels herein is meant hydrocarbon fuels which are gaseous under ambient conditions or light hydrocarbon liquids which become gaseous by preheating. Examples of these fuels are liquefield petroleum gases (LPG) containing propane or butane or mixtures of both, liquefield natural gas (LNG) containing predominantly methane with some ethane but no more than trace quantities of other materials, and natural gas liquids (NGL) which are separated as liquids during the production of natural gas and contain, besides butane and propane, some ethane, pentane and heavier fractions. It is understood that reference herein to propane or LPG is meant to include any or all of the aforementioned gaseous fuels.
Recent discoveries of new sources of such fuels provide the prospect that gaseous fuels are likely to be in adequate supply over the next 10-20 years at prices which could be significantly below that of gasoline.
While gaseous fuels, LPG in particular, have been used with internal combustion engines for a long time, such use has not been on a large scale, largely due to the convenience and readily accessibility of gasoline, as well as the fact that until recently there was no significant price advantage of the gaseous fuel over the liquid fuel.
Due to recent international crises which produced periods of scarcity of gasoline as well as very substantial price increases in the latter fuel, there has developed renewed interest in using gaseous fuels in internal combustion engines, especially in vehicles such as cars, taxicabs and trucks.
All of these events were occurring at the same time that government imposed regulations with respect to mileage and emissions were being issued. Engines were and are becoming more sophisticated in design to meet these requirements including the application of electronic ignition systems and microprocessor control over engine performance.
These developments have made it more difficult to switch from gasoline to gaseous fuels in such vehicles because operating parameters were being altered so that the engineering which went into producing the desired mileage and emission goals could be negated when a new fuel is substituted for gasoline.
Attempts have been made to develop systems which could use gaseous and other alternative fuels in internal combustion engines. Some attempts involve the use of the alternative fuel as a supplement to gasoline under certain operating conditions, and such arrangements are shown in U.S. Pat. Nos. 2,525,576, 2,129,930, 2,657,913, 3,618,579, and 4,181,100.
One of the problems associated with the use of gaseous fuels in internal combustion engines is the tendency for vapor lock to develop if an attempt is made to restart an engine while it is still hot.